If you want to get less oversteer the common suspension practice is to either stiffen up the rear or soften up the front. Since the front is pretty soft on stock form I would try the former not the latter.
I've done a fair bit of experimentation both on the street and the track and found this to be my preference for my WRX. If you only want to street drive it, adjustable swaybar(s) may give you all you need. But if you want to track it or really customize the setup you may want to consider some coilovers.
But don't listen to me Arthur has 10x the experience that I do with suspension setup... and no matter what, AWD cars will exhibit some oversteer if you try to throttle-steer. Not that you can't throttle-steer but it requires a gentle foot. And I've found with my setup that the best way to get the car to rotate is trail braking.